# Mechanical Stability and Clinical Outcomes Following Posterior Cervical Fusion Surgery Using C3-6 Lateral Mass Screw Fixation: En Bloc Versus Regional Screw Fixation

## TL;DR

This study compares two surgical techniques for cervical spine fusion and finds that en bloc fusion reduces mechanical failure without worsening outcomes.

## Contribution

The study demonstrates that en bloc fusion from C2 to C7 provides greater mechanical stability than regional fusion in posterior cervical fusion surgery.

## Key findings

- En bloc fusion had a significantly higher fusion rate compared to regional fusion.
- The mechanical failure rate was significantly lower in the en bloc fusion group.
- Functional scores were similar between the two groups despite differences in range of motion.

## Abstract

Background/Objectives: Although lateral mass screws lower the risk of vertebral artery injury, they are shorter and have a weaker purchase than a pedicle screw, thereby posing the risk of mechanical failure following a ≥3-level posterior cervical fusion (PCF). Therefore, the purpose of this study is to demonstrate that the posterior en bloc fusion of C2-7 is mechanically stronger than shorter, regionally confined posterior fusions of the cervical spine. Methods: We included 178 patients who underwent PCF with ≥3 levels. Patients who underwent PCF that included both C2 and C7 were classified as the en bloc fusion group (EBF group, n = 116), while PCF cases not including these levels were assigned to a regional fusion group (RF group, n = 62). The fusion rate, incidences of mechanical failure, and clinical outcomes were evaluated using univariate analysis between the two groups. Results: The fusion rate was significantly higher in the EBF group than in the RF group (p = 0.038). In contrast, the mechanical failure rate was significantly lower in the EBF group (8/116 [6.9%] vs. 16/62 [25.8%], p = 0.047). Although the ROM was significantly higher in the RF group (p < 0.001), the functional scores did not significantly differ between the two groups. Conclusions: EBF seems to lower the rate of mechanical failure, as well as similar clinical outcomes, compared to RF. When the possibility of mechanical failure is high after PCF, extending the fusion level to C2 and C7 could be considered to minimize mechanical failure, rather than stopping at C3 or C6.